VERY,Very,very easy.
Number Theory
Level
2
What is unit digit of the product of all odd numbers between 7 and 2019 inclusive?
0
5
7
9
This section requires Javascript.
You are seeing this because something didn't load right. We suggest you, (a) try
refreshing the page, (b) enabling javascript if it is disabled on your browser and,
finally, (c)
loading the
non-javascript version of this page
. We're sorry about the hassle.
1 solution
Product = 7 * 9 * 11 * 13 * 15 * ... * 2019
5 * (2n-1) = 5(%10)
Hence, Product % 10 = 5